这是最简单的方法:

#!/bin/sh
cat -

用法:

$ echo test | sh my_script.sh
test

要将stdin分配给变量，您可以使用:stdin =$(cat -)或只是简单的stdin =$(cat)作为操作符是不必要的(根据@mklement0注释)。

要解析标准输入中的每一行，请尝试以下脚本:

#!/bin/bash
while IFS= read -r line; do
  printf '%s\n' "$line"
done

要从文件或stdin中读取(如果参数不存在)，您可以将其扩展为:

#!/bin/bash
file=${1--} # POSIX-compliant; ${1:--} can be used either.
while IFS= read -r line; do
  printf '%s\n' "$line" # Or: env POSIXLY_CORRECT=1 echo "$line"
done < <(cat -- "$file")

Notes: - read -r - Do not treat a backslash character in any special way. Consider each backslash to be part of the input line. - Without setting IFS, by default the sequences of Space and Tab at the beginning and end of the lines are ignored (trimmed). - Use printf instead of echo to avoid printing empty lines when the line consists of a single -e, -n or -E. However there is a workaround by using env POSIXLY_CORRECT=1 echo "$line" which executes your external GNU echo which supports it. See: How do I echo "-e"?

参见:当没有参数传递时如何读取stdin ?在stackoverflow SE

从stdin读入变量或从文件读入变量。

现有答案中的大多数示例使用循环，当它从stdin读取时立即回显每一行。这可能不是你真正想做的。

在许多情况下，您需要编写一个脚本来调用只接受file参数的命令。但是在你的脚本中，你可能也想要支持stdin。在这种情况下，您需要首先读取完整的stdin，然后将其作为文件提供。

让我们看一个例子。下面的脚本打印一个证书的证书详细信息(以PEM格式)，该证书可以作为文件传递，也可以通过stdin传递。

# print-cert script

content=""
while read line
do
  content="$content$line\n"
done < "${1:-/dev/stdin}"
# Remove the last newline appended in the above loop
content=${content%\\n}

# Keytool accepts certificate only via a file, but in our script we fix this.
keytool -printcert -v -file <(echo -e $content)

# Read from file

cert-print mycert.crt

# Owner: CN=....
# Issuer: ....
# ....


# Or read from stdin (by pasting)

cert-print
#..paste the cert here and press enter
# Ctl-D

# Owner: CN=....
# Issuer: ....
# ....


# Or read from stdin by piping to another command (which just prints the cert(s) ). In this case we use openssl to fetch directly from a site and then print its info.


echo "" | openssl s_client -connect www.google.com:443 -prexit 2>/dev/null \
| sed -n -e '/BEGIN\ CERTIFICATE/,/END\ CERTIFICATE/ p' \
| cert-print

# Owner: CN=....
# Issuer: ....
# ....

作为一种变通方法，你可以使用/dev目录下的stdin设备:

....| for item in `cat /dev/stdin` ; do echo $item ;done

我认为这是最直接的方法:

$ cat reader.sh
#!/bin/bash
while read line; do
  echo "reading: ${line}"
done < /dev/stdin

--

$ cat writer.sh
#!/bin/bash
for i in {0..5}; do
  echo "line ${i}"
done

--

$ ./writer.sh | ./reader.sh
reading: line 0
reading: line 1
reading: line 2
reading: line 3
reading: line 4
reading: line 5

每当IFS中断输入流时，回显解决方案就添加新行。@fgm的回答可以稍微修改一下:

cat "${1:-/dev/stdin}" > "${2:-/dev/stdout}"

下面的解决方案从文件读取(如果脚本调用时将文件名作为第一个参数$1)，否则从标准输入读取。

while read line
do
  echo "$line"
done < "${1:-/dev/stdin}"

替换${1:-…}如果定义了，则接受$1。否则，使用自己进程的标准输入的文件名。